1 . Field of the Invention
This invention generally relates to the art of heat deflection testing equipment for measuring tolerance and dimension of a sample under different temperatures.
2 . Background of the Invention
Heat deflection testing equipments are widely used in measure field for getting tolerance and dimension of a sample under varying temperatures. A heat deflection testing equipment usually comprises a temperature controlling case and an optical sensor able to emitting detecting beams. In practical detection, the temperature controlling case includes a temperature controlling unit and a compressed gas controlling unit to control a temperature variation curve, for example a temperature variation curve of the surface mounting technology process, and imitate a temperature situation requested by the sample to be detected. The detecting beams emitted by the optical sensor include incident beams projecting on a datum plane and the sample via a window of the temperature controlling case and reflex beams reflected from the datum plane and the sample. The geometric tolerance can be measured by analyzing the incident beams and the reflex beams.
Please referring to relative references: Japan published patent application JP 2002-107116A and JP 2003-307412A.
The heat deflection testing equipment comprises a temperature controlling case and an optical sensor arranged below the temperature controlling case. The temperature controlling case comprises a base, a cover mounted on the base provide with a heat-resisting window for arranging the sample thereon. The window defines a datum plane for supporting the sample. The cover is connected with a blowing-in pipe thereby the compressed gas from the blowing-in pipe is heated by an infrared lamp in the cover and is spouting out from a nozzle. When the cover is in a closed state, the hot or cold gas from the nozzle spouts towards the sample through the sidewalls of the base. The geometric dimension of the sample can be measured by detecting the beams projected on the sample and the datum plane.
However, the heat deflection testing equipment lies in following problems: firstly, when the temperature controlling case is heated, the hot gas from the nozzle is via the sidewalls of the base which result in the hot gas can not directly spout on the sample; secondly, when the temperature of the temperature controlling case is dropped, the cold blast not only passes the sidewalls of the base but also absorbs heat remained on the infrared lamp. So during the whole imitating process of the temperature situation, the temperature controlling case can not provide quick variety of temperature which decreases the accuracy of the imitating temperature situation.
In addition, in abovementioned heat deflection testing equipment, devices used for detection have to be disposed under the sample, and the sensor is arranged under the temperature controlling case which make heat deflection testing equipment not easy carry and mate with the detecting device, therefore the equipment has a limit detecting scope, and is not able to detect the coefficient of heat expansion and shape distortion. The present invention is directed to solving these problems.